Ram pressure standoff extension and safe/arm mechanism for self-arming munitions

ABSTRACT

A munition for flight through a fluid medium environment to a target having an extendible standoff member normally carried within the munition body for efficient packing density, an interior diaphragm responsive to the differential between fluid ram pressure and local low static pressure during flight to extend the standoff member forwardly of the munition body, and a detonator carried by the standoff member into an armed position wherein it is responsive to the impact of the standoff member with the target to detonate the munition at a predetermined standoff distance from the target.

[ 1 Jan. 16, 1973 n w a P a t S Davis et a1.

1,322,083 11/1919 2,513,185 6/1950 Lauritsen 3,229,638 1/1966 PrimaryExaminer--Samuel W. 'Engle [75] Inventors: Thomas L. Davis; Joseph D.Hansen,

Att0rneyGlenn Orlob and Kenneth M. Maclntosh both of Huntsville, Ala.

[73] Assignee: The

[57] ABSTRACT A munition for flight through a fluid medium environ-Boeing Company, Seattle,

Wash.

ment to a target having an extendible standoff member normally carriedwithin the munition body for efficient packing density, an interiordiaphragm [22] Filed: July 28, 1970 21 App]. No.: 58,807

responsive to the differential between fluid ram pressure and local 10wstatic pressure during flight to exgi fifii tend the standoff memberforwardly of the munition 102/74, 81

[52]v US. int.

body, and a detonator carried by the standoff member intoan armedposition wherein it is responsive to the [58] Field ofSearch...................

impact of the standoff member with the target to [56] References CitedUNITED STATES PATENTS Barlow 102/74 7 Claims, 3 Drawing Figures RAMPRESSURE STANDOFF EXTENSION AND SAFE/ARM MECHANISM FOR SELF-ARMINGMUNITIONS BACKGROUND OF THE INVENTION This invention relates tomunitions designed for flight through a fluid environment to a targetand more particularly to. means for arming such munitions in response toa flight environment forcing function and for detonating the munition ata predetermined standoff distance from the target.

It has long been known that the armor penetration capability of amunition can be increased by appropriately shaping the munition chargegeometry and by detonating the munition at a predetermined distance,known as the standoff distance, from the charge to the armor surface.For conventionally shaped charge geometries, maximum armor penetrationis achieved with a standoff distance of approximately three to fourcharge diameters. Detonation of the charge at the predetermined standoffdistance has been provided in the prior art by affixing to the nose ofthe munition an elongated standoff member which impacts the target priorto the munition proper, and triggers the detonation of the explosivecharge upon the impact of the standoff member with the target. However,providing a standoff member of sufficient length to detonate themunition at an optimum standoff distance seriously compromises thepacking density capability of the munition, resulting in handlingproblems prior to launch and seriously limiting the number of munitionsthat can be carried in a weapons delivery system. With the developmentof submunitions designed to be clustered in the warhead of a missile orother similar weapons delivery system, the packing density of theparticular submunition design becomes a critical factor for effectiveweapon deployment. Thus the weapons designer has been required to make acompromise between optimum standoff distance and maximum packing densitywith the normal compromise generally being for increased packing densityand reducing standoff distance to approximately to one charge diameter.

In addition to the penalty of low packing density, prior art standoffmembers have posed problems in prelaunch handling of the munition. Sincethe munition must be sensitive to detonation by impact force applied tothe standoff member, the extension of this member beyond the normalenvelope of the munition has resulted in increased exposure of themunition to accidental detonation. Thus it is desirable to provide anarming sequence that is responsive to a forcing function obtained onlyin the in-flight environment and to provide a safe condition wherein theexplosive train is discontinuous so the accidental detonation of theinitiator or detonator will not result in detonation of the principalexplosive charge.

When a munition is designed for multiple packing or clustering in awarhead, problems of standoff member damage and premature detonationhave been encountered due to collisions between the submunitions duringthe initial dispersal sequence. Thus it is desirable to not only providean arming sequence responsive to the in-flight environmental conditions,but means must be provided to protect the standoff member and delay thearming sequence for an interval subsequent to warhead opening to preventdisarming of the submunition and to insure against premature detonation.

SUMMARY OF THE INVENTION It is an object of this invention to providemeans for detonating a munition at an optimum predetermined standoffdistance from a target without compromising packing density of themunition.

It is another object of this invention to provide means for arming amunition designed for flight through a fluid environment to a target,said means being responsive to a forcing function obtained only in thein-flight environment.

It is yet another object of this invention to provide a munition havingminimum length for increased packing density and an out-of-lineexplosive train for increased safety during prelaunch handling and whichis responsive to post launch in-flight environment for arming andstandoff extension.

It is a further object of this invention to provide a submunitioncapable of delayed in-flight standoff extension and arming forpreventing premature detonation due to collisions between submunitionsduring initial dispersal sequence.

These and other objects of the invention are provided by incorporatingwithin a munition designed for flight through a fluid medium environmentto a target, an extendible standoff member that is carried within thebody of the munition prior to launch and which, in response to theflight environment, extends forwardly of the munition body to apredetermined optimum standoff distance. Forward movement of thestandoff member is provided by a rearwardly extending conical yieldablediaphragm attached to the standoff member and defining a pair ofchambers within the munition body; one of said chambers being incommunication with the fluid ram pressure at the nose of the munition,and the other chamber being in communication with the fluid staticpressure at a point remote from the nose of the munition. Thedifferential fluid pressure applied to the diaphragm deforms the conicaldiaphragm to a forwardly extending position extending the standoffmember forwardly beyond the nose of the munition. Detonator means,carried by the standoff member, are simultaneously moved from a safeposition, out of line with the explosive train with its impact actuationaxis normal to the longitudinal axis of the standoff member, to an armedposition, in operative relationship with the munitions explosive chargewith the impact actuation axis inclined to and having a substantialcomponent parallel with the longitudinal axis of the standoff member.Upon impact of the standoff member with the target, impact forces aretransmitted to the detonator causing detonation of the munitions chargeat the predetermined optimum standoff distance from the target.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric view, partly insection and with portions broken away, of a munition incorporating thefeatures of the invention in the safe condition with the standoff memberwithdrawn.

FIG. 2 is an isometric view, partly in section and with portions brokenaway, of a munition incorporating the features of this invention in thearmed condition with the standoff member extended.

FIG. 3 is a longitudinal cross sectional view of the forward portion ofthe munition of FIG. 2 showing details of the detonator and standoffextension apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingswhich illustrate a shaped charge munition designed for flight throughthe atmosphere to a target that incorporates the standoff extension andsafe/arm features of the invention, there is shown a housing having fins12 for aerodynamic stability and containing a shaped explosive charge 14with a shaped charge liner 16. While the standoff extension features ofthis invention provide particular benefits when applied to shaped chargemunitions and will be described herein that context, it is to beunderstood that the features of this invention can be applied to otherthan shaped charge munitions. Similarly, the application of thisinvention is not limited to munitions designed for aerodynamic flight toa target, but may also be applied to munitions designed for flightthrough environments other than the atmosphere, such as torpedoes andother underwater munitions.

Housing 10 has a nose cone 18 which is generally hollow and forming aninterior nose cavity defined by the interior surface 19 of nose cone 18and the shaped charge liner 16. A differential pressure sensitive means,such as a conically shaped deformable diaphragm 20 is positioned withinsaid nose cavity with the outer peripheral edge 22 of the diaphragmsealed to the interior wall surface 19 of nose cone 18 forming twoseparate pressure chambers within said nose cavity: a fore or lowpressure chamber 24 defined by diaphragm 20 and interior wall surfaces19 of nose cone l8; and an aft or high pressure chamber 26 defined bydiaphragm 20 and shaped charge liner l6. Attached to the central apex ofconical diaphragm 20 and sealed thereto is elongated standoff means 28which may conveniently be a hollow tubular member having longitudinalaxis 30 and an interior bore 32 communicating with aft chamber 26.Standoff means 28 extends forwardly of diaphragm 20 through fore chamber24 and is slidably fitted to an aperture in forward nose portion 34 ofnose cone 18. It is normally desirable that standoff means 28 be fittedto nose cone 18 such that its longitudinal axis 30 is coincident withthe longitudinal axis of the munition in order to provide aerodynamicstability and to insure that the forward end of standoff means 28 willbe presented to the free stream total pressure field during flightof themunition. A bore or aperture 36 is provided in the shoulder of nose cone18 at a point remote from forward nose portion 34 to vent fore chamber24 to a low fluid pressure region on the order of free stream staticpressure during the flight of the munition through a fluid mediumenvironment.

Collar 38 fixedly attached to standoff means 28 within chamber 24 haspivotally attached thereto a detonator means 39 having a first endcomprising a piston 40 pivotally connected to collar 38 by pin 42;

and a second end comprising a cylindrical sleeve 44 containing adetonating charge 46. As is more clearly shown in FIG. 3, sleeve 44 iscrimped about an annular groove in piston 40 and the end of piston 40opposite to that pinned to collar 42 is formed into a firing pin 48placed adjacent to detonating charge 46. Impact or accelerating forceapplied to detonator means 39 along impact actuation axis 50, which isgenerally the symmetrical axis of detonator means 39 and extends throughpin 42, will cause firing pin 48 to penetrate and detonate detonatorcharge 46.

During storage or while contained within a warhead or other weaponsdelivery system, and at all times prior to launch through the atmosphereor other fluid medium to a target, the munition embodying the apparatusof this invention is in the configuration as shown in F 1G. 1, whereinstandoff means 28 is in a first position contained essentially entirelywithin nose cone. l8 and does not extend forwardly beyond forward noseportion 34 of nose cone 18. Diaphragm 20 is in its relaxed position withthe apex thereof, to which is attached standoff means 28, extendingrearwardly toward shaped charge liner 16 and impact actuation axis 50 ofdetonator means 39 is essentially normal to longitudinal axis 30 ofstandoff means 28 in a safe or unarmed position. This orientation ofimpact actuation axis 50 and longitudinal axis 30 is maintained bycompression springs bias means 52 which may be either a metalliccompression spring or a resilient nonmetallic compression member. Inthis condition the overall length of the munition is at a minimumenabling increased packing density to be obtained in a warhead or otherweapons delivery system. In addition, any impact force. accidentallyapplied to forward nose portion 34 of nose cone 18 will not betransferred to detonator means 39 and cause the detonation thereofbecause of the perpendicular orientation of impact actuation axis 50 andstandoff longitudinal axis 30; and even if detonator .means 39 should beaccidentally detonated, since it is not in operative relationship withshaped explosive charge 14 and is shielded therefrom by diaphragm 20 andshaped charge liner 16, a detonation of the shaped charge would notresult.

Upon warhead opening or other launch of the munition from its deliverysystem into the atmosphere or other fluid medium environment forflightto a target, fins 12 stabilize the flight path of the munition andforward nose portion 34 of nose cone l8 experiences the ram fluidpressure. During the flight of the munition to the target, the fluid rampressure is conducted to aft chamber 26 through interior bore 32 ofstandoff means 28 while simultaneously fore chamber 24 is vented to alow static pressure region remote from forward nose portion 34 causing abuildup of pressure in the aft side of diaphragm 20 and a drop inpressure in the fore side of diaphragm 20. This results in adifferential pressure applied across diaphragm 20 producing a resultantpressure acting on the aft side of diaphragm 20 deforming it in aforward direction, as shown in FIG. 2, to move standoff means 28 to asecond position wherein standoff means 28 extends forwardly beyondforward nose portion 34 of nose cone 18.

As standoff means 28 moves forwardly to the second position duringflight, it carries detonator means 39 along with it into operativerelationship with shaped explosive charge 14 in a manner to be nowdescribed. Positioned on interior surface 19 of nose cone 18 is cammingmeans 54 having a first surface 56 engaging sleeve 44 of the second endof detonator means 39 during movement of standoff means 28 from thefirst to the second position. During this engagement of detonator means39 with first surface 56 of camming means 54,

the bias of spring bias means 52 is overcome and detonator means 39 ispivotally urged about pin 12 from the safe position, wherein its impactactuation axis 50 is normal to standoff means axis 30, to an inclinedarmed position, wherein impact actuation axis 50 has a substantialcomponent parallel to longitudinal axis 30, as is shown more clearly inFIG. 3. As sleeve 44 of the second end of detonator means 39 travelsalong first surface 56 of camming means 54 and reaches the forward endthereof, spring bias means 52 urges detonator means 39 upwardly, asshown in FIG. 3, locking the second end of detonator means 39 intoabutting relationship with second surface 58 of camming means 54. Milddetonating cord 62 connected to booster charge 64 in a well or bore 66within shaped explosive charge M has an end 60 contained within a borein camming means 54 and presented to second surface 58 thereof. In thismanner, forward movement of standoff means 28 from the first position tothe second position by the differential pressure applied to diaphragmduring flight of the munition to a target, moves detonator means 39 froma safe or unarmed position, wherein its impact actuation axis 50 isessentially normal to standoff means axis 30, to an armed position,wherein detonator charge 4-6 is locked into operative relationship withshaped explosive charge 14 and wherein impact actuation axis 50 has asubstantial component parallel to longitudinal axis 30. Upon impact withthe target, a component of the impact force received by standoff means28 is transferred through pin 42 and piston 40, causing firing pin 48 topenetrate detonator charge 46 producing a detonation thereof. Thisexplosive energy is then transferred by mild detonator cord 62 tobooster charge 64 which detonates explosive charge M in a very shortinterval subsequent to the impact of standoff means 28 with the target.

While the optimum standoff distance yielding maximum armor penetrationfor a shaped charge munition depends upon many design factors, includingcharge cone angle, liner material and the type of explosive, there isgenerally an increase in armor penetration with increased standoffdistance up to a certain point for all types of shaped charge munitions.In the case of a munition employing a charge cone angle of 60, maximumarmor penetration is obtained at a standoff distance of approximatelythree to four charge diameters. In order to obtain acceptable packingdensities, munitions employing conventional fixed geometry standoffmeans are limited to standoff distances of approximately one chargediameter thus compromising the armor penetration capability of themunition. By employing the apparatus of this invention, standoff means28 may be readily sized to provide standoff distances on the order of 1V2 3 charge diameters thus providing increased armor penetrationcapability without compromising the packing density of the munition.Increased length of standoff means 28 yielding standoff distances in theorder of d charge diameters may also be employed subject to the flightstability characteristics of the specific munition design and itsintended application.

Differential pressure sensitive means of configurations other thandiaphragm 20, such as a bellows, may be employed in the practice of thisinvention. However, diaphragm 20 is considerably less complicated than abellows arrangement and provides increased economy of manufacture andreliability of operation. In addition, diaphragm 20 has the capabilityof long excursions in response to the fluid ram and static pressuredifferential making possible standoff distances of up to three chargediameters without sacrificing packing density. In certain applications,when such large stan-.

doff distances are not required and the increased complexity sowarrants, a bellows arrangement may be used to replace diaphragm 20.Diaphragm 20 is preferably made of a deformable material such as nylon,Mylar, or other types of plastic films or membranes. Diaphragm 20 mustpossess sufficient yieldability to deform from the stored position, asshown in FIG. 1, to the inverted position, as shown in FIG. 2, in orderto move standoff means 28 from the first to the second position.Diaphragm 20 should also be sufficiently inert to retain itsyieldability over long durations of storage and, in this regard, vacuumformed nylon materials have been found to be particularly suitable.

While the apparatus of this invention has been described as applied to amunition, it is also particularly suitable as applied to a plurality ofsubmunitions, packed into a warhead or other weapons delivery system. Inthis application, it is generally desirable to delay the application ofthe full differential pressure to diaphragm 20 for a duration subsequentto the initial submunition dispersal sequence to prevent damage ofstandoff means 28 or premature detonation of the submunition due tocollisions between the submunitions. This operational delay can beachieved by metering the high fluid ram pressure flow through an orificerestricting interior bore 32 of standoff means 28. In FIGS. 1 and 2,such metering is provided by rolling over the forward end of tubularstandoff means 28 to form an orifice of a diameter less than interiorbore 32. Increased flexibility in providing various operational delaysmay be obtained by the alternate configuration shown in FIG. 3, whereina separate orifice defining plug 68 is inserted into interior bore 32and fixed therein prior to launch of the munitions.

What is provided, then, by this invention is an improved means forarming a munition during flight to a target responsive to a forcingfunction obtained only in the flight environment and for detonating themunition at optimum preselected standoff distances from the target.These advantages are obtained without sacrificing packing densitycapability of the'munition and out-ofline safety of the explosive trainis maintained to prevent accidental detonation prior to in-flightarming. The features of this invention may be applied to a plurality ofsubmunitions clustered. in a warhead, or the like, wherein delayedin-flight arming and standoff extension can be provided to preventpremature detona tion of the submunition during the initial dispersalsequence due to collisions between the submunitions. Variousmodifications of the features of this invention may be resorted to bythose skilled in the art without departing from the spirit and scope ofthe invention as hereinafter defined by the appended claims.

We claim:

ll. In a munition for flight through a fluid medium environment to atarget, improved means for arming the munition and for detonating themunition at a predetermined standoff distance from the targetcomprising:

a. a housing for containing an explosive charge and having a forwardnose' portion;

b. elongated standoff means longitudinally mounted in the nose portionof said housing and adapted for movement from a first position, whereinsaid standoff means is withdrawn into said housing, to a secondposition, wherein said standoff means extends forwardly beyond the noseportion of said housing;

0. differential pressure sensitive means connected to said standoffmeans within .said housing and responsive to the pressure differentialbetween the fluid ram pressure at the forward nose portion and the fluidstatic pressure at a low pressure region remote from the forward noseportion, said differential pressure "sensitive means including adeformable diaphragm means defining fore and aft chambers within saidhousing, and further including means for venting said fore chamber tothe static fluid pressure at a low pressure region remote from theforward nose portion of said housing and means for applying the fluidram pressure to the aft chamber whereby the differential fluid pressurebetween the fore and aft chambers during flight of the munition to thetarget deforms said diaphragm means to move said standoff means from thefirst to the second positions, and

d. detonator means connected to said standoff means for movement therebyinto operative relationship with the explosive charge as said standoffmeans moves from the first to the second positions, said detonatingmeans adapted for detonation of the explosive charge upon impact of saidstandoff means with the target when in the second position.

2. The apparatus as claimed in claim 1 wherein said standoff meanscomprises a hollow tube in fluid pressure communication with the aftchamber for applying the fluid ram pressure to said diaphragm meansduring flight to the target.

3. The apparatus as claimed in claim 2 further including orificedefining means positioned within said hollow tube standoff means fordelaying the application of the fluid ram pressure to said diaphragmmeans during flight to the target.

4. in a munition for flight through a fluid medium environment to atarget, improved means for arming the munition in response to the flightenvironment and for detonating the munition at a predetermined standoffdistance from the target comprising:

a. a housing for containing an explosive charge and having a forwardnose portion;

b. elongated standoff means having a longitudinal axis and slidablymounted in the forward nose portion of said housing, said standoff meanslongitudinally movable from a first position, contained essentiallyentirely within said housing for storage of the munition, to a secondposition, extending substantially beyond the forward nose portion ofsaid housing, for impact with the target prior to such impact of theforward nose portion;

c. detonator means having an impact actuation axis, a first endcontaining a detonating charge, and a second end pivotally connected tosaid standoff means;

(1. spring bias means engaging said detonating means for biasing saiddetonating means to a safe position wherein the impact actuation axis isessentially normal to said standoff means longitudinal axis when saidstandoff means is in the first position;

e. camming means contained within said housing and having a firstsurface engaging said detonating means for overcoming the bias of saidspring bias means and pivotally urging said detonating means to aninclined armed position wherein the impact actuation axis has asubstantial component parallel to said standoff means longitudinal axisas said standoff means is moved from the first to the second positions;said camming means further having a second surface receiving in abuttingrelationship the first end of said detonating means when said detonatingmeans is in the armed position wherein the second surface presents adetonating cord explosive train, connected to the explosive charge, inoperative relationship with the detonating charge; and

f. differential pressure sensitive means connected to said standoffmeans within said housing responsive to the pressure differentialbetween the fluid ram pressure at the forward nose portion and the fluidstatic pressure at a low pressure region remote from the forward noseportion during flight of the munition to the target to move saidstandoff means from the first position to the second position.

5. in a munition for flight through a fluid medium environment to atarget, improved means for arming the munition in response to the flightenvironment and for detonating the munition at a predetermined standoffdistance from the target comprising:

a. a housing for carrying an explosive charge;

b. said housing having a forward nose portion;

c. elongated standoff means slidably mounted in said forward noseportion for movement from a first position within said nose portion to asecond position extending substantially beyond said. forward noseportion;

d. differential pressure sensitive means connected to said standoffmeans within said housing responsive to differential pressure;

e. said differential pressure sensitive means including a deformablediaphragm defining fore and aft chambers within said housing, and meansfor venting said fore chamber to static fluid pressure at a low pressureregion remote from said forward nose portion and means for applying saidfluid ram pressure to said aft chamber whereby the differential of fluidpressure between said fore and aft chambers during flight of munition tothe target deforms said diaphragm for moving said standoff means fromsaid first to said second position, and

f. detonator means having an impact actuation axis, a first endcontaining a detonator charge and a second end connected to saidstandoffmeans for movement of said detonator means from an unarmed to an armedposition in response ,to movement of said standoff means first positionto said standoff means second position respectively, so that said impactactuation axis of said detonator means moves for a substantial componentparallel to said standoff means longitudinal axis in said the fluid rampressure to said diaphragm means during flight to the target.

7. The munition as claimed in claim 6 further including orifice definingmeans positioned within said hollow tube standoff means for delaying theapplication of the fluid ram pressure to said diaphragm means duringflight to the target.

1. In a munition for flight through a fluid medium environment to atarget, improved means for arming the munition and for detonating themunition at a predetermined standoff distance from the targetcomprising: a. a housing for containing an explosive charge and having aforward nose portion; b. elongated standoff means longitudinally mountedin the nose portion of said housing and adapted for movement from afirst position, wherein said standoff means is withdrawn into saidhousing, to a second position, wherein said standoff means extendsforwardly beyond the nose portion of said housing; c. differentialpressure sensitive means connected to said standoff means within saidhousing and responsive to the pressure differential between the fluidram pressure at the forward nose portion and the fluid static pressureat a low pressure region remote from the forward nose portion, saiddifferential pressure sensitive means including a deformable diaphragmmeans defining fore and aft chambers within said housing, and furtherincluding means for venting said fore chamber to the static fluidpressure at a low pressure region remote from the forward nose portionof said housing and means for applying the fluid ram pressure to the aftchamber whereby the differential fluid pressure between the fore and aftchambers during flight of the munition to the target deforms saiddiaphragm means to move said standoff means from the first to the secondpositions, and d. detonator means connected to said standoff means formovement thereby into operative relationship with the explosive chargeas said standoff means moves from the first to the second positions,said detonating means adapted for detonation of the explosive chargeupon impact of said standoff means with the target when in the secondposition.
 2. The apparatus as claimed in claim 1 wherein said standoffmeans comprises a hollow tube in fluid pressure communication with theaft chamber for applying the fluid ram pressure to said diaphragm meansduring flight to the target.
 3. The apparatus as claimed in claim 2further including orifice defining means positioned within said hollowtube standoff means for delaying the application of the fluid rampressure to said diaphragm means during flight to the target.
 4. In amunition for flight through a fluid medium environment to a target,improved means for arming the munition in response to the flightenvironment and for detonating the munition at a predetermined standoffdistance from the target comprising: a. a housing for containing anexplosive charge and having a forward nose portion; b. elongatedstandoff means having a longitudinal axis and slidably mounted in theforward nose portion of said housing, said standoff means longitudinallymovable from a first position, contained essentially entirely withinsaid housing for storage of the munition, to a second position,extending substantially beyond the forward nose portion of said housing,for impact with the target prior to such Impact of the forward noseportion; c. detonator means having an impact actuation axis, a first endcontaining a detonating charge, and a second end pivotally connected tosaid standoff means; d. spring bias means engaging said detonating meansfor biasing said detonating means to a safe position wherein the impactactuation axis is essentially normal to said standoff means longitudinalaxis when said standoff means is in the first position; e. camming meanscontained within said housing and having a first surface engaging saiddetonating means for overcoming the bias of said spring bias means andpivotally urging said detonating means to an inclined armed positionwherein the impact actuation axis has a substantial component parallelto said standoff means longitudinal axis as said standoff means is movedfrom the first to the second positions; said camming means furtherhaving a second surface receiving in abutting relationship the first endof said detonating means when said detonating means is in the armedposition wherein the second surface presents a detonating cord explosivetrain, connected to the explosive charge, in operative relationship withthe detonating charge; and f. differential pressure sensitive meansconnected to said standoff means within said housing responsive to thepressure differential between the fluid ram pressure at the forward noseportion and the fluid static pressure at a low pressure region remotefrom the forward nose portion during flight of the munition to thetarget to move said standoff means from the first position to the secondposition.
 5. In a munition for flight through a fluid medium environmentto a target, improved means for arming the munition in response to theflight environment and for detonating the munition at a predeterminedstandoff distance from the target comprising: a. a housing for carryingan explosive charge; b. said housing having a forward nose portion; c.elongated standoff means slidably mounted in said forward nose portionfor movement from a first position within said nose portion to a secondposition extending substantially beyond said forward nose portion; d.differential pressure sensitive means connected to said standoff meanswithin said housing responsive to differential pressure; e. saiddifferential pressure sensitive means including a deformable diaphragmdefining fore and aft chambers within said housing, and means forventing said fore chamber to static fluid pressure at a low pressureregion remote from said forward nose portion and means for applying saidfluid ram pressure to said aft chamber whereby the differential of fluidpressure between said fore and aft chambers during flight of munition tothe target deforms said diaphragm for moving said standoff means fromsaid first to said second position, and f. detonator means having animpact actuation axis, a first end containing a detonator charge and asecond end connected to said standoff means for movement of saiddetonator means from an unarmed to an armed position in response tomovement of said standoff means first position to said standoff meanssecond position respectively, so that said impact actuation axis of saiddetonator means moves for a substantial component parallel to saidstandoff means longitudinal axis in said second extended position andwhereby said first end detonator charge moves into cooperatingrelationship with means interconnecting said detonating charge with saidexplosive charge carried in said housing, thereby arming said munition.6. The munition as claimed in claim 5 wherein said standoff meanscomprises a hollow tube in fluid pressure communication with the aftchamber for applying the fluid ram pressure to said diaphragm meansduring flight to the target.
 7. The munition as claimed in claim 6further including orifice defining means positioned within said hollowtube standoff means for delaying the application of the fluid rampressure to said diaPhragm means during flight to the target.